Introductory technical guidance for civil engineers, highway engineers and other professional engineers and construction managers interested in design and construction of prestressed post-tensioned box girders for bridge and highway construction. Here is what is discussed: 1. INTRODUCTION, 2. CROSS SECTION PROPERTIES AND SIGN CONVENTION, 3. STRESS SUMMARIES IN A PRESTRESSED BEAM, 4. SELECTION OF PRESTRESSING FORCE FOR A GIVEN ECCENTRICITY, 5. PERMISSIBLE ECCENTRICITIES FOR A GIVEN PRESTRESSING FORCE, 6. EQUIVALENT FORCES DUE TO POST-TENSIONING AND LOAD BALANCING, 7. POST-TENSIONING IN CONTINUOUS GIRDERS, 8. TENDON PROFILESÑPARABOLIC SEGMENTS.